Biocidal compositions and method of treating water using thereof

ABSTRACT

In one embodiment, a method of treating an aqueous system inhibits growth of one or more micro-organisms therein and/or reduces the number of live micro-organisms therein. The method includes adding treatment agents to an aqueous system wherein said treatment agents include a phosphonium compound and a hypohalite compound. In one embodiment, the phosphonium compound includes tri n-butyl n-tetradecyl phosphonium chloride (TTPC) and the hypohalite compound includes sodium hypochlorite.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 14/513,768 filed Oct. 14, 2014, which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to water treatment, particularly thoughnot exclusively, to methods of treating aqueous systems to inhibitgrowth of micro-organisms.

BACKGROUND TO THE INVENTION

The presence and growth of micro-organisms in aqueous systems,especially in industrial water systems, is a concern. Examples ofindustrial water systems where micro-organisms are a concern includecooling water systems, pulping and papermaking systems and oil and gasfield water systems.

The presence of micro-organisms in industrial water systems may resultin the formation of deposits on system surfaces. These deposits or slimecan give rise to various problems. In cooling water systems, slime mayrestrict water flow, reduce heat transfer efficiency, cause corrosionand may be aesthetically unappealing especially if algae are present dueto their visible green pigmentation. Corrosion can also occur inindustrial water systems in the absence of visible slime through theaction of micro-organisms.

In pulp and paper mill systems, slime formed by micro-organisms maycause fouling, plugging, or corrosion of the system. The slime may alsobreak loose and become entrained in the paper produced causingblemishes, holes, tears, and odour in the finished product. The endresult may therefore be unusable product and wasted output.

Slime can also be a problem in oil and gas field water systems and maycause energy losses due to increased fluid frictional resistance,formation plugging and corrosion. The slime may harbour a mixture ofaerobic and anaerobic bacteria that are responsible for the productionof hydrogen sulfide gas. The hydrogen sulfide may cause souring of oiland gas which may reduce the quality of these products and increasetreatment costs.

Pseudomonas aeruginosa bacteria are commonly present in air, water, andsoil. These bacteria continually contaminate open cooling water systems,pulping and papermaking systems and oil and gas field water systems andare among the most common slime formers. Slime may be viewed as being amass of cells stuck together by the cementing action of the gelatinoussecretions around each cell. The slime entraps other debris, restrictswater flow and heat transfer, and may serve as a site for corrosion.

Chlorella vulgaris algae are also commonly present in air, water, andsoil. These algae continually contaminate open cooling water systems andtheir growth turns the water and surfaces in these systems green. Theyalso provide a food source for bacteria, which can stimulate slimeformation, and protozoa which can harbour the pathogenic bacteriumLegionella pneumophila.

A known method of controlling microbial growth in aqueous systems is touse biocides. While biocides are known to inhibit microbial growth, thebiocidel effect is generally of limited duration. The effectiveness ofknown biocides may be rapidly reduced as a result of exposure tonegative influences. Negative influences may include temperature, pH orreaction with ingredients present in the system which neutralizes theirbiocidal effect. Therefore, the use of such biocides may involvecontinuous or frequent addition and their application at multiple sitesor zones in the system to be treated. The cost of the biocide treatmentand the labour costs associated with the application of known biocidesmay therefore be significant.

Known biocides are also highly toxic in the quantities known to berequired for effective control of microbial populations. As a result,the amount of biocide that can be safely discharged into the environmentmay be limited by environmental regulations. Therefore, the need existsfor improved methods for controlling microbial growth in aqueoussystems.

As noted above, known biocides have a number of limitations includingthe large quantities of biocides which typically have to be used toachieve the desired biocidel effect and the potential harmful effects onthe environment of biocides and therefore reducing the amount necessaryfor control and thus the quantity released to the environment has manybenefits.

Accordingly, the present invention aims to address at least onedisadvantage associated with the prior art whether discussed herein orotherwise.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method oftreating an aqueous system as set forth in the appended claims. Otherfeatures of the invention will be apparent from the claims, and thedescription which follows.

According to a first aspect of the present invention there is provided amethod of treating an aqueous system to inhibit growth of one or moremicro-organisms therein and/or to reduce the number of livemicro-organisms therein, wherein the method comprises adding treatmentagents to an aqueous system and wherein said treatment agents comprise:

(a) a phosphonium compound; and(b) a hypohalite compound.

Suitably, the method comprises treating an aqueous system to inhibitgrowth of anaerobic bacteria and/or to reduce the number of liveanaerobic bacteria therein. Suitably, the method comprises treating anaqueous system to inhibit growth of facultative anaerobic bacteriaand/or to reduce the number of live facultative anaerobic bacteriatherein. Suitably, the method comprises treating an aqueous system toinhibit growth of aerobic bacteria and/or to reduce the number of liveaerobic bacteria therein.

The aqueous system to be treated may comprise constituents other thanwater. The aqueous system to be treated may alternatively consist ofwater. Suitably the aqueous system comprises a mixture of water andother constituents. The aqueous system may contain oil. The aqueoussystem may comprise an oil and water emulsion. The aqueous system maycomprise solids. The aqueous system may comprise suspended solids. Theaqueous system may comprise dissolved solids. The aqueous system maycomprise one or more salts, for example sodium chloride.

Suitably, the method comprises a method of treating an aqueous systemcomprising dissolved solids.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 1000 mg l⁻¹ or greater. Suitably, the aqueoussystem has a total dissolved solids (TDS) of at least 2000 mg l⁻¹, forexample at least: 3000 mg l⁻¹; 4000 mg l⁻¹; 5000 mg l⁻¹; 6000 mg l⁻¹;7000 mg l⁻¹; 8000 mg l⁻¹; 9000 mg l⁻¹; or 10,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 10,000 mg l⁻¹ or greater. Suitably, theaqueous system has a total dissolved solids (TDS) of at least 11,000 mgl⁻¹, for example at least: 12,000 mg l⁻¹; for example at least: 13,000mg l⁻¹; 14,000 mg l⁻¹; 15,000 mg l⁻¹; 16,000 mg l⁻¹; 17,000 mg l⁻¹;18,000 mg l⁻¹; 19,000 mg l⁻¹; or 20,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 20,000 mg l⁻¹ or greater. Suitably, theaqueous system has a total dissolved solids (TDS) of at least 21,000 mgl⁻¹, for example at least: 22,000 mg l⁻¹; for example at least: 23,000mg l⁻¹; 24,000 mg l⁻¹; 25,000 mg l⁻¹; 26,000 mg l⁻¹; 27,000 mg l⁻¹;28,000 mg l⁻¹; 29,000 mg l⁻¹; or 30,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 30,000 mg l⁻¹ or greater. Suitably, theaqueous system has a total dissolved solids (TDS) of at least 31,000 mgl⁻¹, for example at least: 32,000 mg l⁻¹; for example at least: 33,000mg l⁻¹; 34,000 mg l⁻¹; 35,000 mg l⁻¹; 36,000 mg l⁻¹; 37,000 mg l⁻¹;38,000 mg l⁻¹; 39,000 mg l⁻¹; or 40,000 mg l⁻¹.

The method may comprise treating an aqueous system having a totaldissolved solids (TDS) of 50,000 mg l⁻¹ or greater. The aqueous systemmay have a total dissolved solids (TDS) of at least 60,000 mg l⁻¹, forexample at least: 70,000 mg l⁻¹; 80,000 mg l⁻¹; 90,000 mg l⁻¹; 100,000mg l⁻¹; 110,000 mg l⁻¹; 120,000 mg l⁻¹; 130,000 mg l⁻¹; 140,000 mg l⁻¹;150,000 mg l⁻¹; 160,000 mg l⁻¹; 170,000 mg l⁻¹; 180,000 mg l⁻¹; 190,000mg l⁻¹; 200,000 mg l⁻¹; 210,000 mg l⁻¹; 220,000 mg l⁻¹; 230,000 mg l⁻¹;240,000 mg l⁻¹; or 250,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 250,000 mg l⁻¹ or less. The aqueous system mayhave a total dissolved solids (TDS) of no more than 240,000 mg l⁻¹, forexample no more than 230,000 mg l⁻¹; 220,000 mg l⁻¹; 210,000 mg l⁻¹;200,000 mg l⁻¹; 190,000 mg l⁻¹; 180,000 mg l⁻¹; 170,000 mg l⁻¹; 160,000mg l⁻¹; 150,000 mg l⁻¹; 140,000 mg l⁻¹; 130,000 mg l⁻¹; 120,000 mg l⁻¹;or 110,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of 100,000 mg l⁻¹ or less. The aqueous system mayhave a total dissolved solids (TDS) of no more than 90,000 mg l⁻¹, forexample no more than 80,000 mg l⁻¹; 70,000 mg l⁻¹; 60,000 mg l⁻¹; 50,000mg l⁻¹; or 40,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of from 10,000 mg l⁻¹ to 250,000 mg l⁻¹.Suitably, the method comprises treating an aqueous system having a totaldissolved solids (TDS) of from 10,000 mg l⁻¹ to 100,000 mg l⁻¹.Suitably, the aqueous system has a total dissolved solids (TDS) of from20,000 mg l⁻¹ to 100,000 mg l⁻¹, for example from 25,000 mg l⁻¹ to100,000 mg l⁻¹. Suitably, the aqueous system has a total dissolvedsolids (TDS) of from 30,000 mg l⁻¹ to 100,000 mg l⁻¹. Suitably, themethod comprises treating an aqueous system having a total dissolvedsolids (TDS) of from 20,000 mg l⁻¹ to 80,000 mg l⁻¹, for example from25,000 mg l⁻¹ to 80,000 mg l⁻¹. Suitably, the method comprises treatingan aqueous system having a total dissolved solids (TDS) of from 30,000mg l⁻¹ to 80,000 mg l⁻¹.

Suitably, the method comprises treating an aqueous system to inhibit thegrowth of a plurality of different micro-organisms.

Suitably, the method comprises treating an aqueous system to prevent thegrowth of one or more micro-organisms. Suitably, the method comprisestreating an aqueous system to prevent the growth of a plurality ofdifferent micro-organisms.

Suitably, the method comprises treating an aqueous system to kill one ormore micro-organisms. Suitably, the method comprises treating an aqueoussystem to kill a plurality of different micro-organisms.

Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of one or more micro-organisms therein and/or toreduce the number of live micro-organisms therein, wherein saidmicro-organisms are selected from bacteria, fungi, and algae. Suitably,the method comprises a method of inhibiting growth of bacteria and/orkilling bacteria. Suitably, the method comprises a method of inhibitinggrowth of fungi and/or killing fungi. Suitably, the method comprises amethod of inhibiting growth of algae and/or killing algae.

Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of anaerobic micro-organisms. Suitably, the methodcomprises treating an aqueous system to kill anaerobic micro-organisms.Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of anaerobic bacteria. Suitably, the method comprisestreating an aqueous system to kill anaerobic bacteria. Suitably, themethod comprises treating an aqueous system to inhibit or prevent thegrowth of facultative anaerobic bacteria. Suitably, the method comprisestreating an aqueous system to kill facultative anaerobic bacteria.

Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of aerobic micro-organisms. Suitably, the methodcomprises treating an aqueous system to kill aerobic micro-organisms.Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of aerobic bacteria. Suitably, the method comprisestreating an aqueous system to kill aerobic bacteria.

Suitably, the method comprises treating an aqueous system to inhibit orprevent the growth of anaerobic and aerobic micro-organisms. Suitably,the method comprises treating an aqueous system to kill anaerobic andaerobic micro-organisms. Suitably, the method comprises treating anaqueous system to inhibit or prevent the growth of anaerobic and aerobicbacteria.

Suitably, the method comprises treating an aqueous system to killanaerobic and aerobic bacteria.

The method may comprise a method of inhibiting growth of gram-positiveaerobic bacteria, gram-positive facultative anaerobic bacteria,gram-negative aerobic bacteria, gram-negative facultative anaerobicbacteria, gram-positive anaerobic bacteria and/or gram-negativeanaerobic bacteria. The method may comprise a method of inhibitinggrowth of mold and/or yeast. The method may comprise a method ofinhibiting the growth of blue green algae and/or green algae. Suitably,the method comprises a method of inhibiting the growth of gram-negativeaerobic bacteria, gram-negative facultative anaerobic bacteria,gram-negative anaerobic bacteria, and green algae. Suitably, the methodcomprises inhibiting the growth of Pseudomonas aeruginosa bacteria in anaqueous system. Suitably, the method comprises inhibiting the growth ofEnterobacter aerogenes bacteria in an aqueous system. Suitably, themethod comprises inhibiting the growth of Desulfovibrio vulgarisbacteria in an aqueous system. Suitably, the method comprises inhibitingthe growth of Chlorella vulgaris algae in an aqueous system.

Suitably, the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous systemsuch that a Log 10 reduction of 4 or greater in an anaerobe culture isobtained after a contact time of 10 minutes. Suitably, the methodcomprises obtaining a Log 10 reduction of 5 or greater to an anaerobeculture after a contact time of 10 minutes. Suitably, the methodcomprises obtaining a Log 10 reduction of 6 or greater to an anaerobeculture after a contact time of 10 minutes.

Suitably, the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous systemsuch that a complete kill of an anaerobe culture is obtained after acontact time of 30 minutes. Suitably, the method comprises obtaining aLog 10 reduction of 5 or greater to an anaerobe culture after a contacttime of 30 minutes. Suitably, the method comprises obtaining a Log 10reduction of 6 or greater to an anaerobe culture after a contact time of30 minutes.

Suitably, the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous systemsuch that a Log 10 reduction of 4 or greater in a facultative anaerobeculture is obtained after a contact time of 10 minutes. Suitably, themethod comprises obtaining a Log 10 reduction of 5 or greater to afacultative anaerobe culture after a contact time of 10 minutes.Suitably, the method comprises obtaining a Log 10 reduction of 6 orgreater to a facultative anaerobe culture after a contact time of 10minutes.

Suitably, the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous systemsuch that a complete kill of a facultative anaerobe culture is obtainedafter a contact time of 30 minutes. Suitably, the method comprisesobtaining a Log 10 reduction of 5 or greater to a facultative anaerobeculture after a contact time of 30 minutes. Suitably, the methodcomprises obtaining a Log 10 reduction of 6 or greater to a facultativeanaerobe culture after a contact time of 30 minutes. The method maycomprise obtaining a Log 10 reduction of 7 or greater to a facultativeanaerobe culture after a contact time of 30 minutes. The method maycomprise obtaining a Log 10 reduction of 8 or greater to a facultativeanaerobe culture after a contact time of 30 minutes.

Suitably, the method comprises adding compound (a) and compound (b) tothe aqueous system such that they are added in a combined amount of from0.1 to 1000 parts by weight per one million parts by weight of saidaqueous system (ppm), for example from 0.1 to 100 ppm.

Suitably, the method comprises adding compound (a) and compound (b) tothe aqueous system such that they are present in a combined amount offrom 0.1 to 1000 parts by weight per one million parts by weight of saidaqueous system (ppm), for example from 0.1 to 100 ppm.

As used herein, all references to ppm refer to parts per million byweight unless stated otherwise.

The method may comprise adding compound (a) and compound (b) to theaqueous system such that they are added in a combined amount of from 0.5to 70 ppm. Suitably, the method comprises adding compound (a) andcompound (b) to the aqueous system such that they are added in acombined amount of from 1 to 60 ppm. Suitably, the method comprisesadding compound (a) and compound (b) to the aqueous system such thatthey are added in a combined amount of from 5 to 55 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system in an amount of at least 0.1 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound in an amount of at least 0.1 ppm.

Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is added in an amount of at least 0.2 ppm.Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is added in an amount of at least 0.3 ppm,for example at least: 0.4 ppm; 0.5 ppm; 0.6 ppm; 0.7 ppm; 0.8 ppm; 0.9ppm; or 1.0 ppm. Suitably, the method comprises adding a phosphoniumcompound to an aqueous system such that it is added in an amount of atleast 1 ppm; for example at least 1.5 ppm; 2.0 ppm; 2.5 ppm; 3.0 ppm;3.5 ppm; 4.0 ppm; 4.5 ppm; 5.0 ppm; 5.5 ppm; or 6.0 ppm. The method maycomprise adding a phosphonium compound to an aqueous system such that itis added in an amount of at least 6 ppm, for example at least: 7 ppm; 8ppm; 9 ppm; 10 ppm; 11 ppm; 12 ppm; 13 ppm; 14 ppm; 15 ppm; 16 ppm; 17ppm; 18 ppm; 19 ppm; 20 ppm; 21 ppm; 22 ppm; 23 ppm; 24 ppm or 25 ppm.The method may comprise adding a phosphonium compound to an aqueoussystem such that it is added in an amount of at least 25 ppm, forexample at least: 30 ppm; 35 ppm; 40 ppm; 45 ppm; or 50 ppm. The methodmay comprise adding a phosphonium compound to an aqueous system suchthat it is added in an amount of at least 55 ppm, for example at least:60 ppm; 65 ppm; 70 ppm; 75 ppm; 80 ppm; 85 ppm; 90 ppm; 95 ppm or 100ppm.

Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is present in an amount of at least 0.2 ppm.Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is present in an amount of at least 0.3 ppm,for example at least: 0.4 ppm; 0.5 ppm; 0.6 ppm; 0.7 ppm; 0.8 ppm; 0.9ppm; or 1.0 ppm. Suitably, the method comprises adding a phosphoniumcompound to an aqueous system such that it is present in an amount of atleast 1 ppm; for example at least 1.5 ppm; 2.0 ppm; 2.5 ppm; 3.0 ppm;3.5 ppm; 4.0 ppm; 4.5 ppm; 5.0 ppm; 5.5 ppm; or 6.0 ppm. The method maycomprise adding a phosphonium compound to an aqueous system such that itis present in an amount of at least 6 ppm, for example at least: 7 ppm;8 ppm; 9 ppm; 10 ppm; 11 ppm; 12 ppm; 13 ppm; 14 ppm; 15 ppm; 16 ppm; 17ppm; 18 ppm; 19 ppm; 20 ppm; 21 ppm; 22 ppm; 23 ppm; 24 ppm or 25 ppm.The method may comprise adding a phosphonium compound to an aqueoussystem such that it is present in an amount of at least 25 ppm, forexample at least: 30 ppm; 35 ppm; 40 ppm; 45 ppm; or 50 ppm. The methodmay comprise adding a phosphonium compound to an aqueous system suchthat it is present in an amount of at least 55 ppm, for example atleast: 60 ppm; 65 ppm; 70 ppm; 75 ppm; 80 ppm; 85 ppm; 90 ppm; 95 ppm or100 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound added in an amount of 5.5 to 7.0ppm, for example 6.0 to 6.5 ppm, for example 6.25 ppm. Suitably, themethod comprises adding a phosphonium compound treatment agent to anaqueous system to provide a treated aqueous system comprising saidphosphonium compound added in an amount of 10 to 15 ppm, for example 12to 13 ppm for example 12.5 ppm. Suitably, the method comprises adding aphosphonium compound treatment agent to an aqueous system to provide atreated aqueous system comprising said phosphonium compound added in anamount of 20 to 30 ppm, for example 23 to 27 ppm, for example 25 ppm.Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound added in an amount of 45 to 55 ppm,for example 48 to 52 ppm, for example 50 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system in an amount of not more than 150 ppm; forexample not more than 120 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound in an amount of not more than 150ppm; for example not more than 120 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound added in an amount of not more than110 ppm. Suitably, the method comprises adding a phosphonium compoundtreatment agent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound added in an amount of not more than100 ppm.

Suitably, the method comprises adding a phosphonium compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound in an amount of not more than 110ppm. Suitably, the method comprises adding a phosphonium compoundtreatment agent to an aqueous system to provide a treated aqueous systemcomprising said phosphonium compound in an amount of not more than 100ppm.

Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is added in an amount of not more than 95ppm, for example not more than 90 ppm; 85 ppm; 80 ppm; 75 ppm; 70 ppm;65 ppm; 60 ppm; 55 ppm; or 50 ppm. The method may comprise adding aphosphonium compound to an aqueous system such that it is added in anamount of not more than 50 ppm, for example not more than 45 ppm; 40ppm; 35 ppm; 30 ppm; 25 ppm; 20 ppm; 15 ppm; or 10 ppm.

Suitably, the method comprises adding a phosphonium compound to anaqueous system such that it is present in an amount of not more than 95ppm, for example not more than 90 ppm; 85 ppm; 80 ppm; 75 ppm; 70 ppm;65 ppm; 60 ppm; 55 ppm; or 50 ppm. The method may comprise adding aphosphonium compound to an aqueous system such that it is present in anamount of not more than 50 ppm, for example not more than 45 ppm; 40ppm; 35 ppm; 30 ppm; 25 ppm; 20 ppm; 15 ppm; or 10 ppm.

Suitably, the method comprises adding a hypohalite compound treatmentagent to an aqueous system in an amount of at least 0.1 ppm.

Suitably, the method comprises adding a hypohalite compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising said a hypohalite compound in an amount of at least 0.1 ppm.

Suitably, the method comprises adding a hypohalite compound to anaqueous system such that it is added in an amount of at least 0.2 ppm.Suitably, the method comprises adding a hypohalite compound to anaqueous system such that it is added in an amount of at least 0.3 ppm,for example at least: 0.4 ppm; 0.5 ppm; 0.6 ppm; 0.7 ppm; 0.8 ppm; 0.9ppm; 1.0 ppm; 1.1 ppm; 1.2 ppm; 1.3 ppm; 1.4 ppm; 1.5 ppm; 1.6 ppm; 1.7ppm; 1.8 ppm; 1.9 ppm; or 2.0 ppm. The method may comprise adding ahypohalite compound to an aqueous system such that it is added in anamount of at least 2.1 ppm, for example at least: 2.2 ppm; 2.3 ppm; 2.4ppm; 2.5 ppm; 2.6 ppm; 2.7 ppm; 2.8 ppm; 2.9 ppm or 3.0 ppm. Suitably,the method comprises adding a hypohalite compound to an aqueous systemsuch that it is added in an amount of at least 5 ppm, for example atleast: 10 ppm; 15 ppm; 20 ppm; 25 ppm; 30 ppm; 35 ppm; 40 ppm; 45 ppm;50 ppm; 55 ppm; 60 ppm; 65 ppm; 70 ppm; 75 ppm; 80 ppm; 85 ppm; 95 ppm;or 100 ppm. Suitably, the method comprises adding a hypohalite compoundto an aqueous system such that it is added in an amount of at least 110ppm; for example at least 120 ppm; 130 ppm; 140 ppm; 150 ppm; 160 ppm;170 ppm; 180 ppm; 190 ppm; 200 ppm; 210 ppm; 220 ppm; 230 ppm; 240 ppmor 250 ppm.

Suitably, the method comprises adding a hypohalite compound to anaqueous system such that free hypohalite is present in an amount of atleast 0.2 ppm. Suitably, the method comprises adding a hypohalitecompound to an aqueous system such that free hypohalite is present in anamount of at least 0.3 ppm, for example at least: 0.4 ppm; 0.5 ppm; 0.6ppm; 0.7 ppm; 0.8 ppm; 0.9 ppm; 1.0 ppm; 1.1 ppm; 1.2 ppm; 1.3 ppm; 1.4ppm; 1.5 ppm; 1.6 ppm; 1.7 ppm; 1.8 ppm; 1.9 ppm; or 2.0 ppm. The methodmay comprise adding a hypohalite compound to an aqueous system such thatfree hypohalite is present in an amount of at least 2.1 ppm, for exampleat least: 2.2 ppm; 2.3 ppm; 2.4 ppm; 2.5 ppm; 2.6 ppm; 2.7 ppm; 2.8 ppm;2.9 ppm or 3.0 ppm.

Suitably, the method comprises adding sodium hypochlorite to an aqueoussystem such that the free sodium hypochlorite in said aqueous system isat least 0.1 ppm; for example at least: 0.2 ppm; 0.3 ppm; 0.4 ppm; 0.5ppm; 0.6 ppm; 0.7 ppm; 0.8 ppm; 0.9 ppm; 1.0 ppm; 1.1 ppm; 1.2 ppm; 1.3ppm; 1.4 ppm; 1.5 ppm; 1.6 ppm; 1.7 ppm; 1.8 ppm; 1.9 ppm; 2.0 ppm; 2.1ppm; 2.2 ppm; 2.3 ppm; 2.4 ppm; 2.5 ppm; 2.6 ppm; 2.7 ppm; 2.8 ppm; 2.9ppm or 3.0 ppm. Suitably, the method comprises adding sodiumhypochlorite to an aqueous system such that the free sodium hypochloritein said aqueous system is from 0.1 ppm to 5.0 ppm, for example from 0.1ppm to 3.0 ppm.

Suitably, the method comprises adding sodium hypochlorite to an aqueoussystem such that the applied amount of sodium hypochlorite is at least0.1 ppm; for example at least: 10 ppm; 20 ppm; 30 ppm; 40 ppm; 50 ppm;60 ppm; 70 ppm; 80 ppm; 90 ppm; 100 ppm; 110 ppm; 120 ppm; 130 ppm; 140ppm; 150 ppm; 160 ppm; 170 ppm; 180 ppm; 190 ppm; 200 ppm; 210 ppm; 220ppm; 230 ppm; 240 ppm; or 250 ppm. Suitably, the method comprises addingsodium hypochlorite to an aqueous system such that the applied amount ofsodium hypochlorite is from 0.1 ppm to 300 ppm, for example from 10 ppmto 250 ppm, for example from 60 ppm to 250 ppm.

Suitably, the method comprises adding a hypohalite compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising free hypohalite in an amount of 1.5 to 2.5 ppm for example2.0 ppm.

Suitably, the method comprises adding a hypohalite compound treatmentagent to an aqueous system to provide a treated aqueous systemcomprising free hypohalite in an amount of not more than 20 ppm.

Suitably, the method comprises adding a hypohalite compound treatmentagent to an aqueous system in an amount of not more than 300 ppm, forexample not more than 250 ppm.

Suitably, the method comprises adding a hypohalite compound to anaqueous system such that free hypohalite is present in an amount of notmore than 15 ppm, for example not more than 10 ppm; 9 ppm; 8 ppm; 7 ppm;or 6 ppm. Suitably, the method comprises adding a hypohalite compound toan aqueous system such that free hypohalite is present in an amount ofnot more than 5.0 ppm; 4.5 ppm; 4.0 ppm; 3.5 ppm; or 3.0 ppm.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina weight ratio of from 1:0.5 to 1.0:50.0, for example 1.0:0.5 to1.0:20.0.

As used herein, all ratios are weight ratios unless stated otherwise.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina weight ratio of from 1.0:0.5 to 1.0:10.0.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of at least 1.0:20.0, for example at least 1.0:10.0, for exampleat least 1:0:5.0.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of no more than 1.0:0.5, for example no more than 1.0:0.7.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of from 1.0:3.0 to 1.0:7.0, for example 1.0:5.6.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of from 1.0:2.0 to 1.0:4.0, for example 1.0:2.8.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of from 1.0:1.0 to 1.0:2.0, for example 1.0:1.4.

Suitably the method comprises adding a phosphonium compound treatmentagent and a hypohalite compound treatment agent to an aqueous system ina ratio of from 1.0:0.5 to 1.0:1.0; for example 1.0:0.7.

The method may comprise adding a combination of phosphonium compounds(a) to an aqueous system. Suitably, the method comprises adding a singletype of phosphonium compound (a) to an aqueous system.

Suitably, the method employs a phosphonium compound (a) having formula:

wherein each R is independently a C₁-C₆ alkyl group which isunsubstituted or substituted by a cyano, hydroxyl, esterified hydroxyl,or aryl group;R¹ represents a C₈-C₁₈ alkyl group which is substituted orunsubstituted; andX represents either chlorine or bromine.

Suitably, each R is a C₁-C₆ alkyl group. Suitably, each R is a C₃-C₅alkyl group. Suitably each R is a butyl group.

Suitably R¹ represents a C₈-C₁₈ alkyl group. Suitably, R1 is a C₁₂-C₁₆alkyl group. Suitably, R¹ is a tetradecyl group.

Suitably, X is chlorine.

Suitably, the method employs a phosphonium compound (a) which is aphosphonium chloride.

Suitably, the method comprises treating an aqueous system such thatphosphonium chloride comprises greater than 50% of the total phosphoniumcompound(s) added to the aqueous system. Suitably, the method comprisestreating an aqueous system such that phosphonium chloride comprisesgreater than 90% of the total phosphonium compound(s) added to theaqueous system, for example 99% or greater.

Suitably, the method comprises treating an aqueous system such thatphosphonium chloride comprises greater than 50% of the total phosphoniumcompound(s) present in the aqueous system. Suitably, the methodcomprises treating an aqueous system such that phosphonium chloridecomprises greater than 90% of the total phosphonium compound(s) presentin the aqueous system, for example 99% or greater.

Suitably, the method employs a phosphonium chloride as the onlyphosphonium compound (a).

Suitably, the method comprises adding tri n-butyl n-tetradecylphosphonium chloride (hereafter “TTPC”) to the aqueous system. Suitably,the phosphonium compound (a) comprises TTPC. Suitably, the phosphoniumcompound (a) consists of TTPC.

Suitably, the method comprises adding an aqueous composition containingthe phosphonium compound (a) to the aqueous system. Suitably, the methodcomprises adding an aqueous composition of TTPC to the aqueous system.The method may comprise adding an aqueous composition comprising 5% byweight of TTPC to the aqueous system. A suitable composition containingTTPC is available from BWA Water Additives and is sold under the tradename Bellacide 355 (an aqueous composition of TTPC and water consistingof water and 5% by weight of TTPC). The method may comprise adding anaqueous composition comprising 50% by weight of TTPC to the aqueoussystem. A suitable composition containing TTPC is available from BWAWater Additives and is sold under the trade name Bellacide 350 (anaqueous composition of TTPC and water consisting of water and 50% byweight of TTPC). Suitably, the method comprises treating an aqueoussystem such that TTPC comprises greater than 50% of the totalphosphonium compound(s) added to the aqueous system. Suitably, themethod comprises treating an aqueous system such that TTPC comprisesgreater than 90% of the total phosphonium compound(s) added to theaqueous system, for example 99% or greater.

Suitably, the method comprises treating an aqueous system such that TTPCcomprises greater than 50% of the total phosphonium compound(s) presentin the aqueous system. Suitably, the method comprises treating anaqueous system such that TTPC comprises greater than 90% of the totalphosphonium compound(s) present in the aqueous system, for example 99%or greater.

Suitably, the method employs TTPC as the only phosphonium compound (a).

The method may comprise adding a combination of hypohalite compounds (b)to an aqueous system. Suitably, the method comprises adding a singletype of hypohalite compound (b) to an aqueous system.

Suitably, the method employs a hypohalite compound (b) comprising ahypochlorite. Suitably, the hypohalite compound (b) consists of ahypochlorite.

Suitably, the method employs a hypohalite compound (b) comprising asodium hypohalite. Suitably, the hypohalite compound (b) consists of asodium hypohalite.

Suitably, the method employs a hypohalite compound (b) comprising sodiumhypochlorite. Suitably, the hypohalite compound (b) consists of a sodiumhypochlorite.

Suitably, the method employs a hypohalite compound (b) which is a sodiumhypochlorite.

Suitably, the method comprises treating an aqueous system such thatsodium hypochlorite comprises greater than 50% of the total hypohalitecompound(s) added to the aqueous system. Suitably, the method comprisestreating an aqueous system such that sodium hypochlorite comprisesgreater than 90% of the total hypohalite compound(s) added to theaqueous system, for example 99% or greater.

Suitably, the method comprises treating an aqueous system such thatsodium hypochlorite comprises greater than 50% of the total hypohalitecompound(s) present in the aqueous system. Suitably, the methodcomprises treating an aqueous system such that sodium hypochloritecomprises greater than 90% of the total hypohalite compound(s) presentin the aqueous system, for example 99% or greater.

Suitably, the method employs sodium hypochlorite as the only hypohalitecompound (b).

Suitably, the method employs a beneficial combination of compounds (a)and (b). The method may employ a synergistic mixture of compounds (a)and (b). Suitably, by “synergistic mixture” it is meant that the mixtureof compounds (a) and (b) has a synergistic effect on the inhibition ofgrowth of one or more biological organisms, preferably micro-organismssuch as bacteria, fungi and/or algae and/or has a synergistic effect onreducing the number of one or more biological organisms, preferablymicro-organisms such as bacteria, fungi and/or algae.

The method may comprise adding compound (a) and compound (b) to theaqueous system such that the aqueous system comprises a synergisticmixture of compounds (a) and (b).

The method may comprise adding compound (a) and compound (b) as amixture to the aqueous system. The method may comprise adding a biocidelcomposition comprising compound (a) and compound (b) to the aqueoussystem. The method may comprise mixing compound (a) and compound (b) andadding the mixture to the aqueous system. Suitably, the method comprisesadding compound (a) and compound (b) separately to the aqueous systemand allowing or causing them to mix within the aqueous system.

Where the method comprises mixing compound (a) and compound (b) andadding the mixture to the aqueous system and/or adding compound (a) andcompound (b) separately to the aqueous system and allowing or causingthem to mix within the aqueous system then compounds (a) and (b) arepreferably used in the form of aqueous compositions.

Suitably, compound (a) is used in the form of an aqueous compositioncomprising between 1% and 90% by weight of compound (a), for examplebetween 1% and 60% by weight. Suitably, compound (a) is used in the formof an aqueous composition comprising between 1% and 10% by weight ofcompound (a), for example 5% by weight.

Suitably, compound (b) is used in the form of an aqueous compositioncomprising between 1% and 90% by weight of compound (b), for examplebetween 1% and 20% by weight. Suitably, compound (b) is used in the formof an aqueous composition comprising between 1% and 10% by weight ofcompound (b), for example 5% by weight.

The method may comprise adding a stabilising agent to the aqueoussystem. The method may comprise adding a stabilised treatment agent tothe aqueous system. The method may comprise adding a treatment agentcomprising compound (a) or (b) and a stabiliser.

The method may comprise a method of treating an industrial water system.The method may comprise treating a cooling water system. The method maycomprise treating a pulping and/or papermaking water system. The methodmay comprise treating an oil and/or gas field water system. The methodmay comprise treating an aqueous system to control the growth ofbacterial and/or algal micro-organisms contained therein and/or whichmay become entrained in said system.

It has been found that the compositions and methods of utilisation ofthe present invention may in particular be efficacious in controllingacid producing facultative anaerobic bacteria and hydrogen sulphideproducing anaerobic bacteria, which may populate aqueous systems.

Surprisingly, it has been found that when treatment agent compounds (a)and (b) are combined the resulting combination may pose a higher degreeof biocidel activity in an aqueous system than that of the individualcompounds used alone. Because of the enhanced activity of thecombination of treatment agent compounds, it may be possible for thetotal quantity of treatment agent added to an aqueous system to bereduced in comparison to a system using only one of said treatment agentcompounds. In addition, the high degree of biocidel activity which isprovided by each of the treatment agent compounds may be exploitedwithout use of higher concentrations of each. The combination of TTPCand sodium hypochlorite may be particularly effective.

It has been found that the compositions and methods of utilisation ofthe present invention may in particular be efficacious in controllingthe facultative anaerobic bacterium Enterobacter aerogenes and/or theanaerobic bacterium Desulfovibrio vulgaris, which may populate aqueoussystems.

Surprisingly, the present inventor has found that mixtures of compounds(a) and (b) such as mixtures of tri-n-butyl n-tetradecyl phosphoniumchloride (TTPC) and sodium hypochlorite are especially efficacious incontrolling the growth of micro-organisms such as bacterial and algalmicrobes in aqueous systems comprising dissolved solids. The efficacy inrelation to acid and sulphide producing bacteria is marked with certainselections of amounts and ratios of components and there is anunexpected synergistic relationship. It has been found that compositionsare unexpectedly effective against anaerobes such as Desulfovibriovulgaris. It has been found that compositions having a weight ratio ofcompound (a):compound (b) of from 1:0.5 to 1:50 may be particularlybeneficial and may have a marked synergy in relation to facultativeanaerobes such as Enterobacter aerogenes.

Surprisingly, the present inventor has also found that the selection ofappropriate amounts and ratios of components provides for stable treatedaqueous systems. Surprisingly, it has been found that aqueous systemswhich are stable at a broad range of temperatures can be provided.

According to a second aspect of the present invention there is provideda method of treating an aqueous system comprising greater than 20,000 mgl⁻¹ total dissolved solids (TDS) to inhibit growth of one or moremicro-organisms therein and/or to reduce the number of livemicro-organisms therein, wherein the method comprises adding treatmentagents to said aqueous system and wherein said treatment agentscomprise:

(a) TTPC; and

(b) sodium hypochlorite.

The method of the second aspect may comprise any feature as described inrelation to the first aspect except where such features are mutuallyexclusive.

According to a third aspect of the present invention there is providedan aqueous system incorporating a combination of:

(i) a phosphonium compound; and(ii) a hypohalite compound.

Suitably, the aqueous system comprises greater than 20,000 mg l⁻¹ totaldissolved solids (TDS).

Suitably, said treatment agent (a) comprises TTPC.

Suitably, said treatment agent (b) comprises sodium hypochlorite.

The aqueous system of the third aspect may comprise any feature asdescribed in relation to one or more of the first and/or second aspectsexcept where such features are mutually exclusive.

According to a fourth aspect of the present invention there is provideda method of inhibiting or preventing the growth of one or moremicro-organisms in an aqueous media, wherein the method comprises addingtreatment agents to an aqueous media and wherein said treatment agentscomprise:

(a) a phosphonium compound; and(b) a hypohalite compound.

Suitably, the aqueous media comprises greater than 20,000 mg l⁻¹ totaldissolved solids (TDS).

Suitably, said treatment agent (a) comprises TTPC.

Suitably, said treatment agent (b) comprises sodium hypochlorite.

The method of the fourth aspect may comprise any feature as described inrelation to one or more of the first and/or second and/or third aspectsexcept where such features are mutually exclusive.

According to a fifth aspect of the present invention there is providedan aqueous media incorporating a combination of:

(i) a phosphonium compound; and(ii) a hypohalite compound.

Suitably, the aqueous media comprises greater than 20,000 mg l⁻¹ totaldissolved solids (TDS).

Suitably, said treatment agent (a) comprises TTPC.

Suitably, said treatment agent (b) comprises sodium hypochlorite.

The aqueous media of the fifth aspect may comprise any feature asdescribed in relation to one or more of the first and/or second and/orthird and/or fourth aspects except where such features are mutuallyexclusive.

According to a sixth aspect of the present invention there is provided abiocidal composition comprising a combination of:

(a) a phosphonium compound; and(b) a hypohalite compound.

Suitably, said treatment agent (a) comprises TTPC.

Suitably, said treatment agent (b) comprises sodium hypochlorite.

The biocidel composition of the sixth aspect may comprise any feature asdescribed in relation to one or more of the first and/or second and/orthird and/or fourth and/or fifth aspects except where such features aremutually exclusive.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be illustrated by way of example withreference to the following preferred embodiments.

Examples

A suspension of Desulfovibrio vulgaris plus Enterobacter aerogenesbacteria containing from 1×10⁶ to 1×10⁸ cells/mL was prepared in sterilepH 7.5 phosphate buffer containing varying levels of sodium chloride togive the desired total dissolved solids (TDS) concentration. Aliquots ofthis suspension were dosed with the indicated concentrations of aphosphonium compound and a hypohalite compound with the concentrationsbeing measured as ppm by weight of the stated compounds added to thedosed suspension. The mixtures were allowed to stand at roomtemperature. At the designated contact times, each mixture was sampledto determine the total number of viable cells of both Desulfovibriovulgaris and Enterobacter aerogenes by serial 10-fold dilution into APIRP 38 media vials and anaerobic acid producing media vials,respectively. The vials were incubated at 37° C. for 72 hours. Resultswere recorded as cells per millilitre.

Aqueous media inoculated with anaerobe and facultative anaerobe cultureand having a TDS of 10,000 mg l⁻¹; 20,000 mg l⁻¹; or 30,000 mg l⁻¹ wastreated with treatment agents comprising: (i) sodium hypochlorite; (ii)tri n-butyl n-tetradecyl phosphonium chloride (TTPC) or (iii) acombination of sodium hypochlorite and TTPC.

TTPC was used in the form of Bellacide 355, an aqueous composition ofTTPC and water consisting of water and 5% by weight of TTPC availablefrom BWA Water Additives.

Sodium hypochlorite was used in the form of Chlorox, an aqueouscomposition of sodium hypochlorite and water consisting of water and 6%by weight sodium hypochlorite available from The Chlorox Company.

The efficacy of the treatment agents was evaluated by measuring the Log10 Reduction of the anaerobe Desulfovibrio vulgaris and the facultativeanaerobe Enterobacter aerogenes [after contact times of 10 and 30minutes as detailed in Table 1. For TTPC and sodium hypochlorite thestated ppm values relate to the amount added. The addition of 35 ppmsodium hypochlorite to the aqueous system provided 2 ppm of free sodiumhypochlorite in the treated aqueous system.

TABLE 1 Log10 Contact Treatment agent (ppm) Log10 Reduction TDS timeSodium Reduction Facultative Example (mg l⁻¹) (minutes) TTPChypochlorite Anaerobes Anaerobes  1 (comparative) 10,000 30 25 — 6 6  2(comparative) 10,000 30 50 — 6 8  3 (comparative) 20,000 30 25 — 3 0  4(comparative) 20,000 30 50 — 6 5  5 (comparative) 30,000 30 50 — 0 0  6(comparative) 30,000 30 — 35 3 3  7 30,000 30 6.25 35 6 5  8 30,000 3012.5 35 4 4  9 30,000 30 25 35 6 5 10 30,000 30 50 35 6 6 11(comparative) 30,000 10 — 35 5 2 12 30,000 10 6.25 35 6 5 13 30,000 1012.5 35 6 6 14 30,000 10 25 35 6 8 15 30,000 10 50 35 6 8

It can be seen from the Examples that with a TDS of 30,000 l⁻¹ mg TTPCalone was ineffective against both the anaerobe Desulfovibrio vulgarsand the facultative anaerobe Enterobacter aerogenes after a contact timeof 30 minutes. Sodium hypochlorite had some efficacy against both theanaerobe Desulfovibrio vulgars and the Facultative Anaerobe Enterobacteraerogenes after contact times of 10 and 30 minutes and with a TDS of30,000 mg l⁻¹. Surprisingly however, despite the fact that TTPC alonewas ineffective at high levels of TDS, aqueous systems treated with acombination of TTPC and sodium hypochlorite exhibited greater reductionof both anaerobes and facultative anaerobes than those treated withsodium hypochlorite alone even with high TDS.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent, or similar purpose, unless expresslystated otherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. A method of treating an aqueous system to inhibit growth of one ormore micro-organisms therein and/or to reduce the number of livemicro-organisms therein, wherein the method comprises adding treatmentagents to an aqueous system and wherein said treatment agents comprise:(a) a phosphonium compound; and (b) a hypohalite compound.
 2. A methodaccording to claim 1, wherein the phosphonium compound comprises trin-butyl n-tetradecyl phosphonium chloride (TTPC).
 3. A method accordingto claim 1, wherein the hypohalite compound comprises sodiumhypochlorite.
 4. A method according to claim 1, wherein the phosphoniumcompound comprises tri n-butyl n-tetradecyl phosphonium chloride (TTPC)and wherein the hypohalite compound comprises sodium hypochlorite.
 5. Amethod according to claim 1, wherein the method comprises treating anaqueous system to inhibit growth of anaerobic bacteria and/or to reducethe number of live anaerobic bacteria therein.
 6. A method according toclaim 1, wherein the method comprises treating an aqueous system toinhibit growth of aerobic bacteria and/or to reduce the number of liveaerobic bacteria therein.
 7. A method according to claim 1, wherein themethod comprises treating an aqueous system to inhibit growth offacultative anaerobic bacteria and/or to reduce the number of livefacultative anaerobic bacteria therein.
 8. A method according to claim1, wherein the method comprises treating an aqueous system having atotal dissolved solids (TDS) of 1000 mg l⁻¹ or greater, and wherein: thephosphonium compound comprises tri n-butyl n-tetradecyl phosphoniumchloride (TTPC); the hypohalite compound comprises sodium hypochlorite;the combination of TTPC and sodium hypochlorite is synergistic and isadded to the aqueous system in amounts configured to inhibit growth ofDesulfovibrio vulgaris and Enterobacter aerogenes and/or reduce thenumber of live Desulfovibrio vulgaris and Enterobacter aerogenes in theaqueous system; the amounts of the synergistic combination of the TTPCand the sodium hypochlorite are selected in a weight ratio of from 1:0.5to 1:50; the amount of TTPC is at least 1 part by weight per one millionparts by weight of said aqueous system (ppm) and the amount of sodiumhypochlorite is at least 1 ppm; and the synergistic combination of theTTPC and the sodium hypochlorite shows greater performance of inhibitinggrowth and/or reducing the number of bacteria than the sum of saidtreatment agents' individual performance.
 9. A method according to claim1, wherein the method comprises treating an aqueous system having atotal dissolved solids (TDS) of 10,000 mg l⁻¹ or greater, and wherein:the phosphonium compound comprises tri n-butyl n-tetradecyl phosphoniumchloride (TTPC); the hypohalite compound comprises sodium hypochlorite;the combination of TTPC and sodium hypochlorite is synergistic and isadded to the aqueous system in amounts configured to inhibit growth ofDesulfovibrio vulgaris and Enterobacter aerogenes and/or reduce thenumber of live Desulfovibrio vulgaris and Enterobacter aerogenes in theaqueous system; the amounts of the synergistic combination of the TTPCand the sodium hypochlorite are selected in a weight ratio of from 1:0.5to 1:50; the amount of TTPC is at least 0.1 parts by weight per onemillion parts by weight of said aqueous system (ppm) and the amount ofsodium hypochlorite is selected such that the free sodium hypochloritein said aqueous system is at least 0.1 ppm; and the synergisticcombination of the TTPC and the sodium hypochlorite shows greaterperformance of inhibiting growth and/or reducing the number of bacteriathan the sum of said treatment agents' individual performance.
 10. Amethod according to claim 1, wherein the method comprises adding saidphosphonium compound to said aqueous system in an amount of at least 0.1ppm, and wherein the method comprises adding said hypohalite compound tosaid aqueous system in an amount of at least 0.1 ppm.
 11. A methodaccording to claim 1, wherein the method comprises adding sodiumhypochlorite to an aqueous system such that the applied amount of sodiumhypochlorite is at least 10 ppm.
 12. A method according to claim 1,wherein the method comprises adding sodium hypochlorite to an aqueoussystem such that the free sodium hypochlorite in said aqueous system isat least 0.1 ppm.
 13. A method according to claim 1, wherein the methodcomprises adding compound (a) and compound (b) to the aqueous systemsuch that they are present in a combined amount of from 0.1 to 1000parts by weight per one million parts by weight of said aqueous system(ppm), and wherein the method comprises adding a phosphonium compoundtreatment agent and a hypohalite compound treatment agent to an aqueoussystem in a weight ratio of from 1:0.5 to 1:50.
 14. A method accordingto claim 1, wherein the aqueous system comprises 20,000 mg l⁻¹ orgreater total dissolved solids (TDS), wherein the phosphonium compoundcomprises tri n-butyl n-tetradecyl phosphonium chloride (TTPC), andwherein the hypohalite compound comprises sodium hypochlorite.
 15. Amethod according to claim 14, wherein: the combination of TTPC andsodium hypochlorite is synergistic and is added to the aqueous system inamounts configured to inhibit growth of Desulfovibrio vulgaris andEnterobacter aerogenes and/or reduce the number of live Desulfovibriovulgaris and Enterobacter aerogenes in the aqueous system; thesynergistic combination of the TTPC and the sodium hypochlorite isselected in a weight ratio of from 1:0.5 to 1:50; the amount of TTPC isat least 1 part by weight per one million parts by weight of saidaqueous system (ppm) and the amount of sodium hypochlorite is selectedsuch that the free sodium hypochlorite in said aqueous system is atleast 0.1 ppm; and the synergistic combination of the TTPC and thesodium hypochlorite shows greater performance of inhibiting growth orreducing the number of bacteria than the sum of said treatment agents'individual performance.
 16. A method according to claim 1, wherein theaqueous system comprises 30,000 mg l ⁻¹ or greater total dissolvedsolids (TDS), the phosphonium compound comprises tri n-butyln-tetradecyl phosphonium chloride (TTPC), the hypohalite compoundcomprises sodium hypochlorite, the amounts of the TTPC and the sodiumhypochlorite are selected in a weight ratio of from 1:0.5 to 1:20, theamount of TTPC is not more than 50 ppm, and the amount of sodiumhypochlorite is not more than 250 ppm.
 17. An aqueous systemincorporating a combination of: (i) a phosphonium compound; and (ii) ahypohalite compound.
 18. The aqueous system of claim 17, wherein saidaqueous system is an aqueous media.
 19. The aqueous system of claim 17,wherein said aqueous system is a biocidal composition.
 20. A method ofinhibiting or preventing the growth of one or more micro-organisms in anaqueous media, wherein the method comprises adding treatment agents toan aqueous media and wherein said treatment agents comprise: (a) aphosphonium compound; and (b) a hypohalite compound.